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  #1  
Old 05-15-2022, 03:11 PM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 2,766
Default High Oil Temp...

Let’s talk Oil Temperature in RV-12 with 912ULS….

I recently discovered a crack in the muffler and was able to find an exact replacement exhaust system with only 70TT. Exhaust system is identical to original that I just replaced and it’s in pristine condition. My 12 is an early SN with muffler located close behind the oil cooler.

Rotax originally allowed using Mobil 4T 10W40 Full Synthetic Oil. I continue to use this oil and now have 750TT with no problem.

With original exhaust I would sometimes see 240F oil temp in climb on a hot day. With new exhaust I see 250F oil temp at 85F OAT. Both CHT and EGT are relatively unchanged at ~ 200F and ~1290F.

I am in contact with Mobil Oil tech support and also Rotax with no definitive answers yet. They say they’ll get back to me in a couple of days, but could be like telling a child “later for sure”.

I’ve been searching the internet (I know… not good idea) and see automotive recommends 230-260F oil temps and I also see where Full Synthetic Oils can tolerate 300F.

250F is approx. mid-range yellow arc on Dynon D180 with Van’s preset limits for Oil Temp.

I observe that oil pressure does not fall off at the high oil temp.

My question… what are max oil temps observed in RV-12 with Rotax 912ULS?

Thank you in advance…..
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 790

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father - CFI) - USAAF 1st Lt. Captain B-17H
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  #2  
Old 05-15-2022, 03:54 PM
seagull seagull is offline
 
Join Date: Dec 2019
Location: Highland, CA
Posts: 513
Default

Jim,
I see 230 on oil temp typically at WOT, 120kts level flight on 80 degree days in SoCal. Easily hit 240 on climb out. At 240 I back off on RPM to 4800 and it will drop down after a few minutes but so does my climb / speed.
I noticed my lower oil line on the engine is 1/16” from the muffler and order the banjo oil line from Aircraft Specialties. I am doing a 100hr engine inspection tomorrow and changing that hose. I use sport 4 oil and have 928 hours on the engine. It runs fine and doesn’t use oil or coolant.
My coolant temps hit 230 on climb out but it comes down fast after leveling off. I have been using Preston’s (lime green) coolant and was told to change to Dexcool (orange). I will do that also on this 100 hr.
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  #3  
Old 05-15-2022, 09:27 PM
RFSchaller RFSchaller is offline
 
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 3,303
Default

Jim,

I flew yesterday in 95F Phoenix. On climb out I hit about 245F oil temp which dropped to 230F in cruise with an OAT of 78F at altitude. This is about a 10F improvement after I trimmed 2 1/2” from the lower cowling aft lip and installed two deflectors to create a low pressure area at the cowling outlet. I previously sent you the pics.

Rich
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  #4  
Old 05-15-2022, 09:49 PM
seagull seagull is offline
 
Join Date: Dec 2019
Location: Highland, CA
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Default

Quote:
Originally Posted by RFSchaller View Post
Jim,

I flew yesterday in 95F Phoenix. On climb out I hit about 245F oil temp which dropped to 230F in cruise with an OAT of 78F at altitude. This is about a 10F improvement after I trimmed 2 1/2” from the lower cowling aft lip and installed two deflectors to create a low pressure area at the cowling outlet. I previously sent you the pics.

Rich
How much altitude did you gain before you hit 245F?
I can easily gain 2000’ on hot days before hitting 240F. My cowl is not trimmed but has been modified to move the oil cooler forward.
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  #5  
Old 05-16-2022, 06:51 AM
DBRuth DBRuth is offline
 
Join Date: Nov 2013
Location: Cumming,GA
Posts: 115
Default Oil temperature

On my aircraft, with that exhaust system installed, the oil temperature on a 90 degree ground temperature day would reach about 240-245 by the time I hit 2500' agl. Then I would throttle back and lower the nose to keep temps from getting higher. I opted for the new exhaust system instead of cowl modification. The new(2016) system has about 3" gap behind the oil cooler and I haven't seen temps any higher than 240 on a full throttle climb to 4000'+ agl. Most times the temperature goes down the higher I climb at wot. When the Bride is with me, I have to find smooth air and sometimes that's around 8500-9500 msl. I operate a little higher altitudes than most RV 12 folks.
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  #6  
Old 05-16-2022, 07:12 AM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,395
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Jim, it might help to modify the air intake of the lower cowl to make it more streamlined. There are some square corners in the fiberglass around the oil cooler. If those areas were filled in, then air coming into the cowl would be concentrated and could flow directly into the oil cooler.
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  #7  
Old 05-16-2022, 11:56 PM
seagull seagull is offline
 
Join Date: Dec 2019
Location: Highland, CA
Posts: 513
Default close call

I think I have found the cause of my high oil temp. Today while doing the 100 hr on the engine I found this (see pic below).
This oil line was re-routed when I installed an oil thermostat from Aircraft Specialty Flightlines about 50 flight hours ago when I put the lower cowl / oil cooler back on I didn't see that it pushed the oil line against the exhaust manifold. This could have ended very bad had it gone on much longer.

I contacted Steve at Aircraft Specialty Flightlines and asked if the hose was salvageable and he suggested replacing it, this was around noon today. Steve didn't have the hose in stock. He was able to make it and get it shipped next day UPS, Wisconsin to California and I will have it tomorrow. The best part is he covered it all under warranty. This was clearly my faulty installation, not a bad product. Unbelievable customer service.

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Last edited by seagull : 05-17-2022 at 08:01 PM.
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  #8  
Old 05-17-2022, 10:21 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
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Default

I added a "Cowl Flap" sort of like a Cessna 180. This is just an experiment to see if it reduces oil temp. Sheet aluminum is held in place with 3M Body Side Molding Tape for testing...

Data point for today's flight: 49F OAT 205F Oil Temp 49F Oil Press

It's supposed to near 90F this weekend, so shouldn't have to wait long to wrap up test....
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__________________
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 790

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father - CFI) - USAAF 1st Lt. Captain B-17H
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  #9  
Old 05-17-2022, 10:52 AM
MMiller MMiller is offline
 
Join Date: Oct 2010
Location: Babylon NY
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Default

Indicated temps read higher than actual on the stock D180 version of the 12. The error will be negligible at the bottom of the scale but can be substantial at the top end. Here’s a simple test, when you are indicating temps high in the yellow arc, momentarily turn the Master Switch OFF and see if the indicated temps drop. The lower value will be closer to the actual temperature.

Note: on the D180 12, turning OFF the Master Switch removes power to the oil pressure sensor and it will indicate zero pressure.

This test will NOT work if your engine is running and the regulator wiring was modified with the C pin jumped to battery voltage.
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  #10  
Old 05-17-2022, 12:23 PM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 2,766
Default

Quote:
Originally Posted by MMiller View Post
Indicated temps read higher than actual on the stock D180 version of the 12. The error will be negligible at the bottom of the scale but can be substantial at the top end.
First I've ever heard of this... Can you elaborate on why this happens and amount of possible error at high end of scale? Inquisitive minds want to know....
__________________
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 790

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father - CFI) - USAAF 1st Lt. Captain B-17H
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